Matrix Diffusion Resistors for Strain Sensor Offset Reduction
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Solution Overview
Problem
Existing strain sensors using semiconductor substrates face significant output offset voltage due to temperature changes and dopant dosage gradients, leading to inaccurate strain measurements.
Innovation Solution
The solution involves arranging diffusion resistors in a matrix configuration, allowing for the connection of multiple resistors in series to form bridge resistors, which reduces the variation in resistance changes caused by temperature and heat distribution, thereby minimizing output offset voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the resistance values of the diffusion resistors are increased to reduce power consumption, then power consumption is reduced, but the area occupied by the resistors increases
Solution Approach 1:
The patent divides the Wheatstone bridge circuit into multiple segments by using series connections of diffusion resistors. Instead of using single large-area resistors, the circuit employs multiple smaller resistors connected in series (e.g., multiple 150Ω resistors to achieve 75KΩ total resistance), which reduces the total area occupied while maintaining the required resistance values for low power consumption.
Solution Approach 2:
The patent transitions from a two-dimensional layout where resistors are placed side-by-side to a series connection arrangement that utilizes the circuit topology dimension. By connecting resistors in series along the current path, the design achieves high resistance values without proportionally increasing the planar area occupied by the resistor elements.
2Ease of manufacture
If the diffusion resistors are disposed at positions away from each other to fit on the semiconductor chip, then the chip layout flexibility is improved, but the output offset voltage increases due to temperature gradients
Solution Approach 1:
The patent segments the bridge resistors into multiple small diffusion resistors that can be disposed in a matrix pattern on the chip. This segmentation allows flexible layout arrangements while maintaining thermal coupling between adjacent resistors, thereby reducing output offset voltage caused by temperature gradients.
Solution Approach 2:
The patent applies local quality by creating groups of diffusion resistors with specific spatial relationships. Resistors that are adjacent in the matrix pattern experience similar temperature conditions, and this local thermal homogeneity is leveraged to cancel out temperature-induced resistance variations in the Wheatstone bridge, reducing output offset voltage.
3Area of stationary object
If the resistance values are kept low to accommodate more resistors on the chip, then the chip area utilization is improved, but power consumption increases
Solution Approach 1:
The patent uses segmentation to create multiple small-value diffusion resistors (e.g., 150Ω each) that can be densely packed on the chip. By connecting these small resistors in series, the circuit achieves the required high total resistance (75KΩ) for low power consumption while utilizing the available chip area efficiently with multiple compact resistor elements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration ensures constant strain on the Wheatstone bridge circuit resistors, preventing output offset due to temperature changes and heat distribution, enhancing the accuracy of mechanical quantity measurements.
Implementation Method 1
a sensor for measuring a mechanical quantity by use of a strain detector formed on the surface of a semiconductor substrate... dependency of a resistance value of the impurity layers, on strain
Implementation Method 2
a Wheatstone bridge circuit (hereinafter referred to as a bridge or a bridge circuit) is formed by use of four impurity layers configured such that current is caused to flow in specific directions, thereby realizing measurement of strain in the specific orientations
Data Source
AI summary
Because of stress occurring due to a change in temperature, and presence of heat distribution on a semiconductor substrate, and a dopant dosage gradient, an offset output occurs to a Wheatstone bridge circuit intended for detection of strain, posing a problem. To solve the problem, diffusion resistors are disposed in the form of a matrix, and bridge resistors Rv1, Rv2 each are formed by selectively connecting diffusion resistors disposed in each odd column, in series with each other, while Rh1, Rh2 each are formed by selectively connecting diffusion resistors disposed in each even column, in series with each other.